On Thursday, Trump's odds fell below 3.0 for the first time. When odds are given as a decimal number, the lower the number is, the more likely the outcome is.

Trump was trading at 4.5 at the start of July, but that price decreased as his Democratic rival, Hillary Clinton, faced increased scrutiny over her use of a private email account.

Clinton was matched at odds as low as 1.26 this summer, but that has been creeping up in recent weeks. On Friday, her odds were 1.63, meaning that while Trump is surging, she is still the clear favourite.

The latest increase in Trump's chance to win the presidency comes after Clinton took time out from her campaign to recover from pneumonia, and the Republican candidate polled well in Ohio, which is seen as a key swing state in this election.

Interestingly, Betfair also says that bets are starting to come in for candidates such as former Democratic candidate Bernie Sanders and Vice President Joe Biden. That is because of a belief that Clinton's poor health may force her to drop out of the race, after which a new Democratic candidate would need to be selected. Biden was matched at 1000 in July, but he is now at just 46.

A spokesperson for Betfair said: "There is now £38.5m traded on the next President market, which is nearly ten times the amount that had been traded on the same market eight weeks prior to the 2012 Presidential Election."

The spokesperson continued:

"The difference with this election is that the race is seemingly still relatively open, with confidence in both party nominees exceptionally low."

"By this point, the market should theoretically be a two-horse race and the percentage likelihood for each candidate should equal 100%."

"But with Joe Biden, Bernie Sanders and Tim Kaine still attracting support in the market, there is clearly a feeling among bettors that anything could happen between now and November 6th."